1. Field
The present invention relates generally to mortise locks, and more particularly to two-point mortise locks used in connection with sliding doors.
2. Description of Art
Mortise locks are well known in the art. A mortise is cut into the edge of a sliding door and a lock devise is securely mounted therein. A keeper is then secured at a corresponding position on a door jamb. Typically, the mortise lock includes a single hook that is rotated between locked and unlocked positions by a snib (locking lever) which engages a cam located within the housing. In some applications a locking cylinder is used on the outside of the housing to actuate the lock mechanism. When the door is closed and the actuator is rotated, the hook rotates out of the lock housing and engages a ledge or other retention structure formed in the keeper, thereby fastening the door in locked relation to the jamb.
To unlock the door, the actuator is again rotated to disengage the hook from the ledge formed in the keeper. The door is then free to be moved relative to the jamb. When in the unlocked position, the hook is generally stowed within the lock housing that is fully positioned within the mortise formed in the edge of the door, thereby protecting the hook and preventing it from inadvertent damage or breakage by being slammed against the keeper or snagged by a person walking through the unlocked, open door.
In the patio door/sliding glass door manufacturing industry, the most commonly used mortise lock is the single point. There are many manufacturers of single point locks and they are all virtually the same. These single point locks are of a standard size, namely, 3¼ inches long (represented by “L” in FIGS. 2A and 2B), by ½ inch wide (represented as “W” in FIGS. 2A and 2C), by 1⅛ inches deep (represented by “D” in FIG. 2B). The cam location (where the snib enters the lock) has a backset (represented by distance “D1” in FIG. 2B) (defined as the distance from the backside of the face plate to the center of the cam) of ¾ inch and is located ⅞ inch from the end of the housing. Therefore, the locks that are manufactured for incorporation into these mortises are correspondingly sized. Because of this size constraint, generally a single lock (or hook) is incorporated into the mortise lock device. Due to the numerous moving parts involved in mortise locks, quality manufacture of single hook locks has been cost effective. Single point locks suffer the drawback, however, of being somewhat easily broken or disengaged by a fairly insignificant force, thus defeating the purpose for which the lock is used.
Multi-point mortise locks are commonly used in Europe and are larger than the single point mortise locks used in the U.S. Accordingly, the mortise locks in Europe are generally of larger dimensions than the single point mortise locks commonly used in the United States. Due to the larger mortise dimensions in Europe, it is an easier task to design a cost effective two-point locking device than in the United States, but the increased security achieved with a two-point lock versus the single point lock is significant.
3. Objects and Advantages
It is therefore a principal object and advantage of the present invention to provide a two-point mortise lock that is of the same dimensions as standard sized single point mortise locks in patio doors.
It is another object and advantage of the present invention to provide a two-point mortise lock that can be retrofit into existing mortises.
It is a further object and advantage of the present invention to provide a two-point mortise lock that is durable and can withstand repeated usage.
Other objects and advantages of the present invention will in part be obvious, and in part appear hereinafter.